I am 23 years old and regularly do cardio exercises on the bicycle. Ocassionally I get about 1, maybe 2 feelings of a missed heartbeat during this form of exercise.

My doctor gave me an echocardiogram, showed my heart to be in perfect health. She also gave me 2 EKGs, both fine. I asked for a stress test but she said it wasn't necessary. But what are these palpitations and do other people experience them? They mostly occur when I am doing high intensity cardio, and they don't stop me from continuing they simply startle me.